1. Field of the Invention
The present invention relates to a printing system, a printing apparatus, and a printing method that create and control image data digitally to form an image on a paper. More specifically, the present invention relates to a printing system, a printing apparatus, and a printing method that output image data after subjecting it to gamma correction processing.
2. Description of the Related Art
Calibrations in a printing apparatus, such as a printer, are normally performed in the form of updating of processing parameters in color conversion processing, such as output gamma correction processing. More specifically, the above-mentioned processing is performed generally using a gamma correction table (also called a lookup table “LUT”) and calibrations are performed by updating the table data. Then, in order to update the table data, a series of processing steps to perform calibrations, such as a step of outputting a predetermined image (for example, patch) by a printing apparatus, a target of the calibrations, and a step of reading the image optically, is required (for example, Japanese Patent Laid-Open No. 2001-018498).
A printing apparatus that performs calibrations independently is also known. In particular, in a printing apparatus that adopts an electronic photographing system, calibrations can be performed comparatively easily. Specifically, it is not necessary to output a patch on a printing paper but, for example, a toner image of a predetermined number of patches is formed on a transfer drum and then the toner image is read by an optical sensor provided in advance, and based on the read result, calibration data is created.
Calibrations in such a printing apparatus are performed automatically when, for example, parts, such as a photosensitive drum, are replaced with others, or when environmental parameters such as temperature and humidity change by a predetermined amount or more. It is also possible for a user to perform calibrations at an arbitrary timing.
However, when a gamma correction table is updated by calibrations, pages having already been subjected to gamma correction processing before the calibrations are printed as they are. In this case, those printed pages have not been subjected to appropriate gamma correction processing at that point of time, and therefore, there arises a problem that the printed matter has poor images.